This invention relates to a centrifuge container cap and, more particularly, to a centrifuge container cap which provides an improved cap compression seal.
Among the many types of centrifuges available are those wherein the centrifuge rotor is provided with a plurality of cavities arranged to receive containers or tubes in which samples are to be processed. When the centrifuge is in operation the sample material within the tubes is subjected to centrifugal forces according to the spin speed of the rotor. As the tube's contents are subjected to centrifugal force, there is the ever present problem of the tube's contents migrating upwardly and leaking around the tube cap. Any leaking fluids, of course, are ejected from the tube during the centrifuge operation.
Such leakage is a particular problem if the tubes are positioned with their axis in a vertical orientation. Partly for this reason, centrifuge rotors often are designed with their cavities oriented at an angle with respect to the rotor axis such that the bottom of the tube is at a greater radial distance from the spin axis than the top of the tube. Even with this positioning, since it is necessary to fill the tubes with the fluid up to the very top in order to prevent tube collapse, it is again apparent that sample tries to force its way out through or around the cap.
Accordingly, various caps have been designed for use with centrifuge tubes. These caps provide for a minimum air space and facilitate the complete and total filling of the tubes with a fluid such that the fluid itself acts as a support for the walls of the tube. It has become customary in recent years to use thin-walled plastic tubes for this purpose on a throwaway basis. It is characteristic of these prior art centrifuge caps to use O-rings, Quad X-rings and/or plastic washers for sealing purpose. Caps of this type are described for example in U.S. Pat. No. 3,459,369, issued Aug. 5, 1969 to Lloyd C. Marks, in U.S. Pat. No. 3,635,370, issued Jan. 12, 1972 to William A. Romanauskas, and U.S. Pat. 3,447,712 issued June 3, 1969 to Maurice Galasso et al.
While the caps provided by these patents have proven quite satisfactory, there have been instances in which some of the caps tend to leak. Such leaking, if it occurs, can ruin many days of work; or in the extreme situation, if harmful solutions are being used, possibly endanger the centrifuge operator. There is also a practical problem presented by the cap failure. In the extreme case the cap may become so distorted that it is incapable of disassembly. In this instance, the cap, which is reusable--only the tubes normally are thrown away--must be discarded.
A still further disadvantage of these prior art caps is that with the utilization of O-rings, washers and the like, the number of parts necessary to make a complete cap is increased and hence the cost of the cap is increased.
Accordingly, it is an object of this invention to obviate many of the disadvantages of the prior art centrifuge tube caps.
Another object of this invention is to provide an improved centrifuge tube cap.
A further object of this invention is to provide an improved centrifuge tube cap which is of relatively low cost.